Element for connecting a flexible conductor and method for connecting a flexible conductor to a connection terminal

ABSTRACT

A junction between a flexible conductor and a connection terminal is disclosed. The junction includes a connection terminal that is shaped substantially like a parallelepiped and has an upper face and a lower face, a pair of side faces and an end face. The connection terminal includes, on the end face, one or more slots shaped substantially like a parallelepiped, which run through the entire thickness of the connection terminal. The junction further includes at least one flexible conductor, in which one end part is shaped so as to mate substantially with the inner walls of the slots. The end part of the flexible conductor is inserted in the slots and cold coined, and the flexible conductor protrudes substantially at right angles from one of the upper, lower or end faces. At least one laser welding bead runs across the two slots along two of the faces from which the flexible conductor does not protrude.

DESCRIPTION

The present invention relates to an element for connecting flexibleconductors, particularly for low-voltage circuit breakers andcontactors, and to a method for connecting a flexible conductor,particularly one or more braids, to a connection terminal, particularlyto a connection terminal of a moving contact of a low-voltage circuitbreaker or contactor, by laser welding.

Electric circuit breakers and contactors are normally provided with aflexible conductor, which functionally connects a moving contact and astationary contact. The methods of the background art for providing thejunctions of the flexible conductor with the moving contact and with thestationary contact are normally based on braze-welding processes.

These processes generate high temperatures for relatively long times ina relatively large area around the welding region. This causes annealingof the conductor, which is generally made of copper, with a consequentreduction and deterioration of the mechanical characteristics of theflexible conductor, which inevitably leads to a reduction in the usefullife of the entire circuit breaker or contactor, requiring complicatedmaintenance operations or even the replacement of the devices.

The part of the connection terminal that surrounds the welding region,both on the moving contact and on the stationary terminal, is alsosubjected to the annealing action caused by the heat, with consequentdeterioration of the mechanical properties of these components.

Moreover, these processes require a very intensive use of energy and areexpensive, scarcely flexible and bulky.

However, it is difficult to find an alternative to these methods thatcan be performed industrially, since it is a matter of coupling elementsthat have an irregular shape. For example, in the case of the junctionbetween the conducting braids and the connection terminal of the movingcontact, it is necessary to give the connection both a sufficientmechanical stability and the necessary electrical conductivity by usingin the best possible manner the usable surfaces of the terminal, andthis is not always easy in view of the shape characteristics of thebraid. Furthermore, the dimensions of the flexible conductor and of theconnection terminal can also be relatively large and accordingly thewelding system must have an adequate power level.

Ultrasound welding, for example, does not have the annealing drawbackscited above, but is not practical to use in view of its known powerlimits.

It is evident from the above description that in the background artthere is the need to have systems for connecting flexible conductorswith rigid elements that are a valid alternative to connections obtainedby means of conventional braze welding methods. It is also evident thatin the background art there is the need to have an efficient method forconnecting flexible conductors, particularly copper braids, toconnection terminals.

The aim of the present invention is to provide a junction between aflexible conductor and a connection terminal that has high mechanicalstability and high electrical conductivity and can be manufacturedefficiently.

Within the scope of this aim, an object of the present invention is toprovide a method for connecting a flexible conductor to a connectionterminal that does not cause degradation of the mechanical properties ofthe conductor and/or of the connection terminal.

Another object of the present invention is to provide a method forconnecting a flexible conductor to a connection terminal that ensureshigh electrical conductivity.

Another object of the present invention is to provide a junction betweena copper braid and a connection terminal in a low-voltage circuitbreaker or contactor.

Another object of the present invention is to provide a method forconnecting a copper braid to a connection terminal in a low-voltagecircuit breaker or contactor.

Another object of the present invention is to provide a method forconnecting a flexible conductor to a connection terminal, and a junctionbetween a flexible conductor and a connection terminal, that is simpleto apply industrially, at modest costs and in an economicallycompetitive manner.

This application also lends itself to the use of currently widespreadlow-cost robotized handling units, which introduce great new advantagesin terms of flexibility and programmability in a field that up to nowwas considered extremely inflexible. These characteristics allow, forexample, to treat with the same welding station a very different rangeof connectors and terminals.

This aim, these objects and others that will become better apparent fromthe description that follows and from the accompanying drawings areachieved by means of a junction between a flexible conductor and aconnection terminal, characterized in that it comprises:

-   -   a connection terminal that is shaped substantially like a        parallelepiped and has an upper face and a lower face, two side        faces and an end face; said end face having one or more slots        shaped substantially like a parallelepiped, which run through        the entire thickness of said connection terminal;    -   at least one flexible conductor, in which one end part is shaped        so as to mate substantially with the inner walls of said slots;        said end part being inserted in said slots, and said flexible        conductor protruding substantially at right angles from one of        said upper, lower or end faces;    -   at least one laser welding bead, which runs along said        connection terminal at said slots along at least one of the two        faces from which said flexible conductor does not protrude.

Another aspect of the present invention is a method for providing ajunction between a flexible conductor and a connection terminal,characterized in that it comprises the steps that consist in:

-   -   providing a connection terminal that is substantially shaped        like a parallelepiped and has an upper face and a lower face,        two side faces and an end face, said connection terminal having,        on said end face, one or more slots shaped substantially like a        parallelepiped which run through the entire thickness of said        connection terminal;    -   providing at least one flexible conductor in which one end part        is shaped so as to substantially mate with the inner walls of        said slots;    -   inserting and cold-coining said shaped end part in said slots,        so that said flexible conductor protrudes substantially at right        angles from one of said upper or lower or end faces of said        connection terminal;    -   subjecting, at said slots, at least one of the faces not        affected by the protrusion of said flexible conductor to a        welding action of laser means in order to mutually weld said        connection terminal and said flexible conductor.

It has in fact been found that by using the junction according to theinvention and the method according to the invention, connectionscharacterized by high mechanical stability and high electricalconductivity are provided. The user of laser welding means, moreover,avoids the annealing problems of the background art, consequentlypreserving the mechanical properties of the individual parts.

The characteristics of the method according to the present inventionwill become better apparent with reference to the description thatfollows and to the accompanying drawings, given merely by way ofnon-limitative example, and wherein:

FIG. 1 is a schematic perspective view of a connection terminal and ofthe flexible conductors according to the present invention; and

FIG. 2 is a schematic perspective view of a junction between flexibleconductors and a connection terminal according to the invention, and ofa method according to the invention for providing said junction.

With reference to FIG. 1, the elements that constitute the junction area connection terminal 1, which is shaped substantially like aparallelepiped, with an upper face 11 and a lower face 12, two lateralfaces 13 and 14 and an end face 15. The connection terminal has, on theend face 15, one or more substantially parallelepipedal slots 150, whichrun through the entire thickness of the connection terminal. Inpractice, it can be said that the end face 15 has, in the example, asquare-wave profile.

A second element that constitutes the junction is a flexible conductor2, which has an end part 21 that is shaped so as to mate substantiallywith the inner walls of the slots 150.

With reference to FIG. 2, it is shown that the junction according to theinvention is constituted by the end part 21 of the conductor 2 that isinserted in the slots 150. The flexible conductor 2 in this caseprotrudes substantially at right angles from the lower face 12 of theconnection terminal 1.

Again with reference to FIG. 2, at least one laser welding bead 3 runsalong the connection terminal 1 at the slots 150 along the end face 15and/or along the face that lies opposite the one from which the flexibleconductor protrudes. In the case of FIG. 2 there are laser welding beads3 both along the end face 15 and along the upper face 11.

The term “welding bead” designates the molten material generated by thescanning of laser means along preset lines.

Preferably, and as shown schematically in FIGS. 1 and 2, the flexibleconductor 2 is constituted by one or more copper braids. As describedmore clearly hereinafter, the shaped end part 21 of the flexibleconductor 2 can be obtained conveniently by compressing said braid.

Especially when the junction is relatively large, it is preferable toprovide multiple laser welding beads 3; in this case, it is convenientto have said beads run both along the end face and, for example and withreference to FIG. 2, along the face 11, which in this case is the facethat lies opposite the face 12 from which the flexible conductors 2protrude.

The junctions according to the invention are applied conveniently forexample in low-voltage circuit breakers and contactors. Said circuitbreakers and contactors, in their most schematic form, comprise at leastone moving contact, a flexible conductor, and a connection terminal.

The junctions between the moving contact and the flexible conductor, andbetween the flexible conductor and the connection terminal, can beconstituted conveniently by a junction according to the presentinvention. Said circuit breakers and contactors constitute a furtheraspect of the present invention.

Another aspect of the present invention relates to a method forproviding a junction between a flexible conductor and a connectionterminal and is described in detail hereinafter. With reference to FIGS.1 and 2, the method according to the invention comprises the followingsteps. A connection terminal 1 shaped substantially like aparallelepiped is prepared which has an upper face 11, a lower face 12,two side faces 13 and 14 and an end face 15; one or more slots 150shaped substantially like a parallelepiped are provided on the end face15 and run through the entire thickness of said connection terminal.Moreover, a flexible conductor 2 is provided which has an end part 21that is shaped so as to substantially mate with the inner walls of saidslots.

The shaped end part 21 is inserted and cold-coined in the slots 150, sothat the flexible conductor 2 protrudes substantially at right anglesfrom one of said upper, lower or end faces of the connection terminal,for example from the lower face 12.

With reference to FIG. 2, the end face 15 and/or the lower face 12 aresubjected to the welding action of laser means 40 (shown schematically)to provide a weld between the connection terminal and the flexibleconductor.

As mentioned, the flexible conductor is preferably constituted by one ormore copper braids, and the shaped end part is obtained by compressingsaid braid.

The welding action is preferably obtained by virtue of the scanning oflaser means on the faces 15 and/or 11 or 12, along a direction that issubstantially perpendicular to the lateral faces 13 and 14 of theconnection terminal. In any case, particularly for relatively largejunctions, it is preferable to have the laser means perform multiplescans both on the end face 15 and on the face 11 or 12, along directionsthat are substantially perpendicular to the lateral faces of theconnection terminal.

It is evident to the person skilled in the art that said scanning can beperformed by means of a relative movement of the laser means withrespect to the components to be welded during the welding operation.Said relative movement in practice can be provided by keeping motionlessthe components to be welded and moving the laser means, or by keepingmotionless the laser means and moving the components to be welded, or bymoving both.

The scanning speed, the angle of incidence and all the other physicalparameters of the laser beam described in greater detail hereinafter canbe chosen and modulated according to the characteristics of the elementsto be welded, such as for example their chemical nature or theirthickness, but can also be controlled and changed appropriately duringthe welding operations in order to compensate for the heating of theaffected regions and in general in order to optimize the results.

Although it is possible to use laser means of a different type, it ishighly preferable to use a solid-state laser, for example a Nd crystallaser. In this case also, the operating characteristics of the laser,such as for example its frequency, power and angle of incidence,scanning speed and angle of incidence, can be chosen and modulated as afunction of the characteristics of the elements to be welded and of theresults to be obtained.

In practice, it has been found that by using the method according to theinvention it is possible to obtain junctions that are excellent in termsof mechanical and electrical properties. In particular, the problems ofcopper annealing typical of braze welding processes are avoided. Inpractice, the extremely high electrical conductivity given bycold-coining of the flexible conductors on the connection terminals issafeguarded even after the welding process according to the invention,thus avoiding the deterioration in conductivity that is instead typicalof junctions subsequently subjected to the braze welding process. Laserwelding is left the task of stabilizing the system mechanically and ofpreventing the thermal expansions of the materials in operatingconditions from compromising the electrical conductivitycharacteristics.

Furthermore, the use of laser means allows to avoid applications of heatthat would be critical and harmful for the mechanical characteristics ofthe individual components.

The method according to the invention is furthermore suitable for beinginserted in automated production cycles, allowing for example to obtaincircuit breakers, contactors and components of circuit breakers andcontactors efficiently and relatively cheaply.

In practice, it has been found that the junctions according to theinvention, as well as the method for obtaining them, fully achieve theintended aim and objects.

The junction and the method thus conceived are susceptible of numerousmodifications and variations, all of which are within the scope of theinventive concept; all the details may furthermore be replaced withother technically equivalent elements.

In practice, the materials used, as well as the contingent shapes anddimensions, may be any according to the requirements and the state ofthe art.

1. A junction between a flexible conductor and a connection terminal,wherein the junction comprises: a connection terminal that is shapedsubstantially like a parallelepiped and has an upper face and a lowerface, a pair of side faces and an end face; said connection terminalhaving, on said end face, one or more slots shaped substantially like aparallelepiped, which run through the entire thickness of saidconnection terminal; at least one flexible conductor, in which one endpart is shaped so as to mate substantially with the inner walls of saidslots; said end part being inserted in said slots and cold coined, andsaid flexible conductor protruding substantially at right angles fromone of said upper, lower or end faces; at least one laser welding bead,wherein said at least one laser welding bead runs across said slotsalong two faces among said upper face, said lower face, said pair ofside faces and said end face from which said flexible conductor does notprotrude.
 2. The junction according to claim 1, wherein said flexibleconductor is constituted by a copper braid.
 3. The junction according toclaim 2, wherein the end part of said flexible conductor is shaped bycompressing said braid.
 4. The junction according to claim 1, whereinsaid at least one laser welding bead comprises a plurality of laserwelding beads that run along said two faces.
 5. A low-voltage circuitbreaker or contactor, comprising at least one moving contact, a flexibleconductor, a connection terminal, a first junction between said movingcontact and said flexible conductor, a second junction between saidflexible conductor and said connection terminal, wherein at least one ofsaid first and second junctions is a junction according to claim
 1. 6.The junction according to claim 2, wherein said at least one laserwelding bead comprises a plurality of laser welding beads that run alongsaid two faces.
 7. The junction according to claim 3, wherein said atleast one laser welding bead comprises a plurality of laser weldingbeads that run along said two faces.
 8. A low-voltage circuit breaker orcontactor, comprising at least one moving contact, a flexible conductor,a connection terminal, a first junction between said moving contact andsaid flexible conductor, a second junction between said flexibleconductor and said connection terminal, wherein at least one of saidfirst and second junctions is a junction according to claim
 2. 9. Alow-voltage circuit breaker or contactor, comprising at least one movingcontact, a flexible conductor, a connection terminal, a first junctionbetween said moving contact and said flexible conductor, a secondjunction between said flexible conductor and said connection terminal,wherein at least one of said first and second junctions is a junctionaccording to claim
 3. 10. A low-voltage circuit breaker or contactor,comprising at least one moving contact, a flexible conductor, aconnection terminal, a first junction between said moving contact andsaid flexible conductor, a second junction between said flexibleconductor and said connection terminal, wherein at least one of saidfirst and second junctions is a junction according to claim
 4. 11. Amethod for providing a junction between a flexible conductor and aconnection terminal, wherein the method comprises: providing aconnection terminal that is shaped substantially like a parallelepipedwith an upper face and a lower face, a pair of lateral faces and an endface, said connection terminal having, on said end face, one or moreslots that are shaped substantially like a parallelepiped and runthrough the entire thickness of said connection terminal; providing atleast one flexible conductor in which an end part is shaped so as tosubstantially mate with the inner walls of said slots; inserting andcold-coining said shaped end part in said slots, so that said flexibleconductor protrudes substantially at right angles from one of saidupper, lower or end faces of said connection terminal; subjecting, atsaid slots, two faces among said upper face, said lower face, said pairof lateral faces and said end face from which the flexible conductordoes not protrude to the welding action of laser means to provide a weldbetween said connection terminal and said flexible conductor, whereinsaid weld extends across said slots along said two faces.
 12. The methodaccording to claim 11, wherein said flexible conductor is constituted byat least one copper braid.
 13. The method according to claim 12, whereinthe shaped end part of the flexible conductor is obtained by compressingsaid braid.
 14. The method according to claim 11, wherein said lasermeans scan said two faces along a direction that is substantiallyperpendicular to the lateral faces of said connection terminal.
 15. Themethod according to claim 14, wherein said laser means perform multiplescans on said two faces along directions that are substantiallyperpendicular to the lateral faces of said connection terminal.
 16. Themethod according to claim 11, wherein said laser means are constitutedby a solid-state laser.
 17. A junction between a flexible conductor anda connection terminal, wherein the junction is obtained with a methodaccording to claim
 11. 18. The method according to claim 12, whereinsaid laser means scan said two faces along a direction that issubstantially perpendicular to the lateral faces of said connectionterminal.
 19. The method according to claim 13, wherein said laser meansscan said two faces along a direction that is substantiallyperpendicular to the lateral faces of said connection terminal.
 20. Themethod according to claim 12, wherein said laser means are constitutedby a solid-state laser.
 21. The method according to claim 13, whereinsaid laser means are constituted by a solid-state laser.
 22. The methodaccording to claim 14, wherein said laser means are constituted by asolid-state laser.
 23. The method according to claim 15, wherein saidlaser means are constituted by a solid-state laser.
 24. A junctionbetween a flexible conductor and a connection terminal, wherein thejunction is obtained with a method according to claim
 12. 25. A junctionbetween a flexible conductor and a connection terminal, wherein thejunction is obtained with a method according to claim
 13. 26. A junctionbetween a flexible conductor and a connection terminal, wherein thejunction is obtained with a method according to claim
 14. 27. A junctionbetween a flexible conductor and a connection terminal, wherein thejunction is obtained with a method according to claim
 15. 28. A junctionbetween a flexible conductor and a connection terminal, wherein thejunction is obtained with a method according to claim 16.